switching relay

[highland]

What is a universal switching relay. What is its function. And how do you test to see if its faulty. Thanks.
PS. For an electric ac/heat unit.

[Wgoodrich]

Normally a heat pump / ac unit will have a double bulb thermostat about 2 degrees difference from each other. The first heat bulb will turn on the heat pump but the electric or gas assist heating unit will only turn on the fan to pass across the A coil inside the furnace affected by the heat pump. However the heat pump if an Air to Air heat pump will only maintain a house temp without falling inside the house temp to about 30 degrees outside. When it gets colder outside the heat pump gets over powered in need to produce enough heat. When this happens the bulbs in the thermostat when about 2 degrees falls enough will make contact through the secone bulb in the themostat telling the assist furnace that a the heat pump needs help. When that second bulb makes contact it produces a 24 volt power to a magnetic coil of that universal contactor pulling in the contacts that are rated in amps high enough to carry the load of the heating coils through those isolated contacts of that universal relay.

Apply 24 volts to the magentic coil. The coil should pull in closing those independent contacts. if this happens the the universal contactor is fine and probably a problem in your signal wires in you thermostat or going to your thremostat. If the contactor does not pull in when 24 volts is applied to the magnetic coil of that contactor then you have a bad coil on that contactor.

If your contactor pulls in but no heat is produced you have normally three problems that can cause this. Bad heating elements, no power to the heating elements [tripped breaker or blown fuse] or you have a bad connection in the contactor points or wiring.

Hope this gives you some help

Wg